Radiofrequency (RF) ablation is a widely accepted method to focally destroy cancer of the liver, kidney, bone, and lung. RF can be applied in a minimally invasive fashion, resulting in rapid patient recovery and low morbidity. A substantial problem with RF ablation is the lack of multiple-electrode capability. In this proposal, we will create a multiple-electrode prototype system for use with an experimental high power RF generator, optimize the system, and characterize the system in vivo. This project should greatly increase the effectiveness of RF ablation by decreasing treatment failures, procedure length, and anesthetic complications associated with the protracted treatments often necessary in clinical settings. The specific aims of this proposal are: 1. Design and build a system to operate up to four electrically independent electrodes from an experimental high power RF generator by rapidly switching between electrodes. 2. Optimize the high-power switching system to maximize the ablation zone size by varying applied power and number of electrodes. 3. A) Evaluate the ability to create a highly tumoricidal thermal environment through simultaneous operation of multiple switched electrodes placed in close proximity to each other. B) Test the ability of the proposed system to simultaneously create multiple zones of ablation when the electrodes are widely spaced. 4. Use computer modeling, and in vivo liver experiments to determine the effectiveness of multiple- electrode RF ablation in the perivascular area. To accomplish these aims, an experienced multidisciplinary team at the University of Wisconsin, with collaborators at Harvard University and Valleylab, has been assembled.